Automotive vehicles have for some years now incorporated mandated evaporative fuel emissions control systems. Such systems typically include a canister with a charge of fuel vapor adsorbent material which is mounted to the vehicle body, most often under the hood. A tank line runs from the tank to the canister to store vapors produced in the tank as it sits, generally called the diurnal loss. A purge line runs from the canister to the engine manifold for stored vapor disposal. The tank line may be quite lengthy, especially if the canister is mounted under the hood. New standards have been proposed to also require the control and storage of fuel vapors displaced from the tank as it is filled, which have just been sent to atmosphere in the past. Vehicle systems upgraded to handle fuel fill losses have become known as on-board systems to distinguish them from other systems proposed to handle the fuel fill losses at the filling station instead. Most proposed on board systems block the exit of fuel fill vapors at the filler neck with a control valve, generally referred to as a TVVA, and route the blocked vapors to the same canister, with another vapor line. The vapor line from the TVVA to the canister will be as long or longer than the tank to canister line. A more serious design constraint with on board systems is that canister capacity and size may have to be greatly increased, because of the large volume of displaced fuel fill vapors, leading to under hood packaging difficulties.